Ivan Contreras

Hub-and-Spoke Networks

Hub location problems constitute a challenging class of NP-hard optimization problems lying at the heart of network design planning in transportation systems, namely in the airline and trucking industries. In these systems, hub-and-spoke architectures are usually employed to efficiently route commodities between many origins and destinations. The performance of these systems can be improved by using consolidation points, called hub facilities, where a large number of origin/destination pairs are connected by using a small number of links.

General Network Design

Location analysis and network design have emerged as two major research areas in network optimization. Location problems typically involve siting facilities at nodes of a network whereas network design consists of activating some of the links. In both cases the aim is to ensure cost-effective flows between pairs of nodes to satisfy user demands. General network design problems offer a unified view of these two streams of research. These problems involve design decisions, which are to locate facilities and to activate links in an underlying network, and operational decisions, which are to allocate customers to facilities and to route the users demands.

Dynamic Facility Location-Network Design Problems

In order to develop more realistic models of facility location-network design we must incorporate common features of industrial applications such as their dynamic (or multi-periodic) nature. That is, scenarios (costs, demand, resources, etc.) often vary over the planning horizon. Applications of these type of models customarily appear when modifying already established transportation networks through mergers, acquisitions and divestments of companies. Other applications arise in the design of telecommunication networks in which the aim is to design an optimal evolution of a network, between an existing situation and a forecast target.